1. Field of the Invention
The invention relates to technology for regulating the temperature inside of a power storage device.
2. Description of the Related Art
In recent years, electric vehicles and hybrid vehicles and the like that are provided with an electric motor for driving the vehicle have been receiving attention as environmentally friendly vehicles. The electric motor is driven by electric power output from a battery having a plurality of unit cells that are rechargeable.
Also, with a battery such as a lithium-ion battery, the original energy of the battery is unable to be output in a low-temperature environment. On the other hand, in a high-temperature environment, the battery life becomes shorter. Therefore, the battery is preferably maintained at a temperature of approximately 10° C. to 40° C.
As technology related to this kind of temperature regulation, Japanese Patent Application Publication No. 7-226229 (JP 7-226229 A) describes a high-temperature battery insulating container. In this high-temperature insulating container, when the high-temperature battery generates heat, a thermal insulation panel is raised by a cylinder device and the insulation thickness of a ceiling portion of a vacuum insulation wall is decreased to reduce the insulation performance of the insulating container and promote the dissipation of heat. The heat dissipated from the insulation wall is converted into electricity using a thermoelectric power generating element that is mounted to the vacuum insulation wall, and the energy produced using this wasted heat is used to activate the cylinder device at this time.
In order to regulate the temperature as described above, when simply using heat insulating material, in summer, the temperature inside a battery case does not easily become high but is difficult to cool, so the temperature inside the battery case is often higher than the outside air temperature. On the other hand, in winter, the temperature inside the battery case does not easily become low and does not easily become high due to the heat insulating material, so the temperature inside the battery case is often lower than the outside air temperature.
Also, throughout the day, a vehicle is generally left stopped for a longer time period than a time period in which the vehicle is kept running. Regulation of the battery temperature must be considered even when the vehicle is left stopped or the battery is in long-term storage. However, with JP 7-226229 A, electric power needs to be supplied, making it difficult to deal with situations in which the vehicle is left stopped or the battery is in long-term storage.